obviously those of us who are watching this footage over and over again of a bomb going off in a civilian environment, it looks huge, but can we get a perspective on the size and power of the bomb? how we might compare to to those in a war zone, ieds or military ordnance? >> that's the analysis going on now. the people i've talked to who are doing that seat of the pants comparison say it's not huge. of course, it does look huge. over 100 people injured, that seems frightening. it is, but they were right around it, they were very close to it, crowded around, which you assume is the reason the devices were placed there. it does seem they were intended to cause a maximum amount of casualties, injuries and deaths. where they were placed, when they were placed, and how they were constructed with the additional shrapnel to amp up the injuries. >> pete, over the course of the day, obviously you get a lot of conflicting reports, some of which are not true, but we heard at least some tentative reports about the strategic placement of the devices, whether they might have been put in trash cans or mailboxes or